Re: Has anyone made their own servos from DC Motors?

Hi Les,

I think I know which motors you are referring to. They have a round
flange on the front but also have a bracket for base mounting. They
are somewhat Gold in color and have a 1/2"-13 left hand thread on
the large output shaft?

I have one of those motors I just got working for a high speed
spindle I designed/built for my CNC router. Even at 3:1 pulley
ratio to get the RPMs up, the motor still has plenty of power for
driving the cutter. This is what got me to thinking I could use
these motors for servos.

You say this combination worked well on both Geckos and Rutex. Was
one easier than the other to setup and get running good?

Are the 200 line encoders good enough, or would you prefer to have a
higher resolution?

TIA

Chris








--- In CAD_CAM_EDM_DRO@yahoogroups.com, Les Newell <lesnewell@h...>
wrote:

> Hi Chris,
>
> I used 110V treadmill motors from Surplus Center on my Bridgeport

Series

> 1 mill. The motors have a handy flange on the front that can be

used for

> mounting. Surplus center also sell a very small servo motor with a

200

> line encoder. I used the encoders off of these on the treadmill

motors.

> They work very well with Gecko or Rutex drives and I am extremely
> pleased with the results.
>
> I haven't yet got round to making up covers for the rear of the

motors

> but I must remedy that soon. Having exposed encoders on a mill is

a

> recipe for disaster.
>
> Les
>
> lcdpublishing wrote:
>
> >Has anyone made servos (that work well) from DC motors? I am not
> >sure but unless I am missing something, it seems very possible to

do

> >and affordable too.
> >
> >There are a host of 90 Volt DC treadmill motors out there for

very

> >cheap ($20.00 ~ $50.00). While the claimed HP is 2.5, I suspect
> >they are more close to 3/4 ~ 1 HP, which should be fine for small
> >servos on a home shop machine.
> >
> >Most of these motors have a small shaft on the back end which is
> >usually for a fan blade of some sort. This could be used to

attach

> >a rotary encoder with relative ease. Rotary encoders can be
> >purchase new from US Digital for around $35.00.
> >
> >This gets you a motor and encoder for less than $100.00
> >
> >Next up is an enclosure of sorts for the motor to make it

suitable

> >for use in a metalworking shop. This could be any form of

aluminum

> >from square tubing to round tubing (if the id matches the od of

the

> >motor). Incorporating a flange for mounting should also be

pretty

> >easy to do. I suspect this would add another $40.00 or so.
> >
> >In the end, you could have a decent sized servo for around

$140.00

> >give or take a few bucks.
> >
> >I don't know what else is different about a servo than from what

was

> >just described (I am sure they are little more heavy duty for
> >industrial use). The electricals is something I am unsure of.
> >Encoders are encoders - that isn't much of a problem. But not

all

> >DC motors are the same (I am guessing).
> >
> >Has anyone done this and how did it work out for you? Any
> >suggestions on what type of motor to use or avoid? What about a
> >servo driver, Gecko or other?
> >
> >TIA
> >
> >Chris
> >
> >
> >
> >
> >
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